CN109269830B - Method and system for measuring circulation multiplying power of vertical steam generator of pressurized water reactor nuclear power station - Google Patents
Method and system for measuring circulation multiplying power of vertical steam generator of pressurized water reactor nuclear power station Download PDFInfo
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Abstract
The invention discloses a method for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station, which comprises the following steps: injecting a proper amount of tracer into a second unit loop, and enabling the tracer to circularly flow along the second unit loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system; after the circulation is stabilized, respectively measuring the concentration of the tracer at the upper part, the lower part and the water feeding inlet of the steam generator; and calculating to obtain the circulation multiplying power of the steam generator according to the measured concentration of the tracer. The invention also discloses a system for measuring the circulation multiplying power of the vertical steam generator of the pressurized water reactor nuclear power station. The invention can improve the accuracy and the safety of the measurement of the circulation multiplying power and has good economy.
Description
Technical Field
The invention relates to the technical field of nuclear power stations, in particular to a method and a system for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station.
Background
The steam generator has the main function of transferring heat in coolant in the primary loop to feed water in the secondary loop as heat exchange equipment, and when the steam-water mixture on the secondary side rises along the height of the tube bundle, the heat transferred from the primary loop is continuously received by the heat transfer tubes of the steam generator to evaporate to form steam for the steam turbine to do work. Each loop is fitted with a steam generator and each capacity is designed to deliver one third of the reactor thermal power when operating at full power. Meanwhile, as a device for connecting the first loop and the second loop, the steam generator also forms a second protective barrier for preventing radioactive leakage between the first loop and the second loop. At present, the domestic pressurized water reactor nuclear power station mainly uses a vertical steam generator. The secondary side of the steam generator pushes water circulation by means of the medium gravity difference of the descending channel and the ascending channel, the designed working pressure is generally 3.0-7.0 MPa, the steam-water gravity difference is large, and natural circulation flow is formed.
The circulation rate of the steam generator is the ratio of the flow of the low-heat water at the inlet of the secondary side tube bundle of the steam generator to the flow of the steam at the outlet of the steam generator, and is an important characteristic parameter of the steam generator. A sufficient circulation multiplying power is needed in a secondary side water circulation loop of the steam generator to guarantee stable flow in operation, prevent corrosion of a heat transfer pipe and improve reliability of the steam generator, and the design is generally 3-5. Whether the circulation multiplying power is reasonable is one of indexes for measuring the structural design of the steam generator, so that the accurate measurement of the circulation multiplying power of the steam generator has important significance.
At present, two methods, namely a mass balance method and an enthalpy balance method, are used for measuring the circulation rate of the steam generator.
(1) A mass balance method: the mass flow of water in the descending channel is obtained by measuring the water speed in the descending channel, namely the mass flow is the secondary side tube bundle inlet under-heated water flow (G), and the steam generator outlet steam flow (D) can be obtained by measuring the main water supply flow. The primary element of the main water supply flow measurement adopts a standard orifice plate, and the secondary element is a differential pressure transmitter. The cycle multiplying power is K ═ G/D. However, the measurement of the water velocity in the descent passage of this method is calculated by measuring the differential pressure with a differential pressure transmitter using 3 velocity measurement tubes circumferentially arranged at a distance of about 500mm from the exit of the descent passage. And because the water velocity of the descending channel is too low, the differential pressure measured by the differential pressure transmitter connected with the 3 speed measuring tubes is very small, and the data phase difference measured by the 3 speed measuring tubes is also larger, the precision of the circulation multiplying power measured by a mass balance method is poorer, and only can be used for reference.
(2) Enthalpy equilibrium method: a method for measuring the flow (G) of the low-heat water at the inlet of a secondary side tube bundle of a steam generator and the flow (D) of the steam at the outlet of the steam generator by using a mass balance method; measuring principal feedwater pressure and temperature to determine principal feedwater enthalpy value (i)f) (ii) a Measuring the steam generator head pressure to determine the saturated water enthalpy value (i)w) (ii) a Measuring inlet temperature and pressure of the downcomer channel to determine enthalpy (i) of the principal feedwater after hydrophobic mixing with the steam-water separatormz). According to the enthalpy balance relation D (K-1) iw+Dif＝KDimzAnd obtaining a circulation multiplying factor value. However, the method needs to install a large number of thermal measuring points and measuring instruments such as temperature, pressure, differential pressure, water level, flow rate and the like on the steam generator body, and the measuring cost is high; some thermal measuring points need to be opened on the steam generator body so as to be convenient for installationA pressure guide pipe and a problem sleeve are arranged, so that the strength of the steam generator is reduced, and the operation safety is reduced; moreover, the steam generator is positioned in a nuclear reactor control area, and during the running of the unit with power, the use and maintenance of the measuring points need to enter the control area, which may cause harm to the life safety of running or testing personnel; the installation of a pressure guide pipeline, a temperature sleeve and the like on a steam generator of an in-service unit is carried out under the condition of overhaul of the unit or other shutdown, is related to nuclear safety, and cannot be guaranteed to be carried out at any time. In the enthalpy balance relation, the amount of steam entering the descent passage is not considered (i.e., the lower entrainment coefficient is assumed to be 0), and the steam generator actually has a certain lower entrainment coefficient, which brings certain errors to the calculation and reduces the accuracy of the measurement.
Disclosure of Invention
The invention provides a method and a system for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station, aiming at the problems in the prior art, and the method and the system can improve the accuracy and the safety of the measurement of the circulation multiplying power and have good economy.
The technical scheme provided by the invention for the technical problem is as follows:
on one hand, the invention provides a method for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station, which comprises the following steps:
injecting a proper amount of tracer into a second unit loop, and enabling the tracer to circularly flow along the second unit loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system;
after the circulation is stabilized, respectively measuring the concentration of the tracer at the upper part, the lower part and the water feeding inlet of the steam generator;
and calculating to obtain the circulation multiplying power of the steam generator according to the measured concentration of the tracer.
Further, injecting a proper amount of tracer into the second unit loop to make the tracer circularly flow along the second unit loop, specifically comprising:
and injecting a tracer agent into a condensate pump inlet of the condensate system or a pipeline of a feedwater flow control system between the feedwater system and the steam generator through a high-pressure injection pump, so that the tracer agent is carried by moisture in saturated steam after entering the steam generator, enters a steam turbine, flows to the feedwater system and then enters the steam generator again for circulation.
Further, the measurement method further includes:
sampling and detecting the concentration of the tracer at a drain tank of a steam-water separation reheater system and a pipeline of a condensed water extraction system, and tracking the change trend of the concentration of the tracer;
and after the concentration of the tracer is stable, judging that the tracer circulates in the second loop of the unit to be stable.
Furthermore, after entering the steam generator, the main feed water provided by the water supply system and carrying the tracer flows along the descending channel together with the circulating water carrying the tracer, turns to enter the ascending channel after reaching the tube plate and is heated and evaporated, the tracer is concentrated in the saturated water which is not evaporated, the saturated water which is not evaporated is separated and returned to form the circulating water, and the circulating water continuously flows together with the entering main feed water;
after the circulation is stabilized, the tracer concentrations at the upper part, the lower part and the water feeding inlet of the steam generator are respectively measured, and the method specifically comprises the following steps:
after the circulation is stable, sampling the circulating water at the upper part of the steam generator, the water at the outlet of the descending channel and the main feed water at the feed water inlet respectively;
and respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water.
Further, the sampling of the circulating water at the upper part of the steam generator, the moisture at the outlet of the descending channel and the main feed water at the feed water inlet respectively includes:
communicating a sampling pipeline of a nuclear sampling system in a nuclear power station to an outlet of the descending channel, and sampling moisture at the outlet of the descending channel;
switching a sampling pipeline of the nuclear sampling system to the upper part of the steam generator to sample the circulating water;
sampling the main feed water on a high feed water main pipe through a feed water chemical sampling system in the nuclear power station; the high-pressure water supply main pipe is communicated with a water supply inlet of the steam generator.
Preferably, the tracer is a sodium, lithium, potassium or cesium ion;
after the tracer is injected, the increase in the conductivity of the cations in the steam generator is less than a zone control value of a unit chemistry operating specification.
Further, the measuring the concentrations of the tracer in the circulating water, the outlet moisture of the descending channel and the main feed water respectively specifically comprises:
and respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water by adopting an inductively coupled plasma mass spectrometry.
Further, the calculating to obtain the circulation rate of the steam generator according to the measured concentration of the tracer specifically includes:
and calculating to obtain the circulation multiplying power of the steam generator according to the measured concentration of the tracer and based on a tracer mass balance method.
Further, the formula of the tracer mass balance method is as follows:
WfCf+WrCw＝WeCb；
We＝Wr+Wf；
the calculation formula of the circulation multiplying power of the steam generator is as follows:
wherein K is the circulation multiplying power of the steam generator, WmsMain steam flow, WeFor lowering the water flow at the outlet of the channel, WrFlow rate of circulating water, WfIs the main water supply flow rate CbIn the water at the outlet of the descending channelConcentration of tracer, CwAs tracer concentration in the circulating water, CfIs the concentration of the tracer in the main feedwater.
On the other hand, the invention provides a system for measuring the circulation rate of a vertical steam generator of a pressurized water reactor nuclear power station, which can realize all the processes of the method for measuring the circulation rate of the vertical steam generator of the pressurized water reactor nuclear power station, and the system comprises:
the tracer injection module is used for injecting a proper amount of tracer into the secondary unit loop to enable the tracer to circularly flow along the secondary unit loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system;
the tracer concentration measuring module is used for respectively measuring the tracer concentrations at the upper part, the lower part and the water feeding inlet of the steam generator after circulation is stable;
and the circulation multiplying power calculation module is used for calculating and obtaining the circulation multiplying power of the steam generator according to the measured concentration of the tracer.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
through injecting appropriate amount of tracer in unit two return circuits, treat that circulation is stable after at steam generator upper portion, lower part and water supply line department sample test, acquire the tracer concentration, and then calculate and obtain steam generator's circulation multiplying power value, realize carrying out the accurate measurement of steam generator circulation multiplying power to the nuclear power unit of being in service at any time, can avoid effectively the safety hazard to unit and testing personnel, reduce the measurement cost, have the characteristics of security, economic nature, advance and convenience.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for measuring a circulation rate of a vertical steam generator of a pressurized water reactor nuclear power plant according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a unit secondary loop in the method for measuring the circulation ratio of the vertical steam generator of the pressurized water reactor nuclear power plant according to the first embodiment of the invention;
fig. 3 is a schematic structural diagram of a steam generator in a method for measuring a circulation rate of a vertical steam generator of a pressurized water reactor nuclear power plant according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a system for measuring a circulation ratio of a vertical steam generator of a pressurized water reactor nuclear power plant according to a second embodiment of the present invention.
Detailed Description
In order to solve the technical problems that the circulation multiplying power of a steam generator cannot be accurately and safely measured in the prior art, the invention aims to provide a method for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station, which has the core idea that: a proper amount of tracer is injected into a unit secondary loop, and after circulation is stable, sampling detection is carried out on the upper portion, the lower portion and a water supply pipeline of the steam generator to obtain the concentration of the tracer, so that the circulation rate value of the steam generator is obtained through calculation. The embodiment can improve the accuracy and the safety of the circulation multiplying power measurement, and has good economical efficiency.
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Example one
Referring to fig. 1, an embodiment of the present invention provides a method for measuring a circulation rate of a vertical steam generator of a pressurized water reactor nuclear power plant, where the method includes:
s1, injecting a proper amount of tracer into the unit two loop, and enabling the tracer to circularly flow along the unit two loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system;
s2, after the circulation is stabilized, respectively measuring the concentration of the tracer at the upper part, the lower part and the water feeding inlet of the steam generator;
and S3, calculating and obtaining the circulation multiplying power of the steam generator according to the measured concentration of the tracer.
It should be noted that the two-circuit unit (turbine circuit) mainly includes a steam generator, a turbine, a condensate system and a water supply system. Specifically, as shown in fig. 2, the second loop of the unit is a loop formed by a steam generator 1, a steam turbine 2, a condenser 3, a condensate pump 4, a main water feed pump 5, and pipelines, heaters and valves therebetween, and the working principle of the second loop is that water in the steam generator is heated to be steam, a turbonator is pushed to work, heat energy is converted into electric energy, the steam after work is sent into a condenser to be cooled into condensate water, the condensate water is returned to the steam generator through the condensate pump and the main water feed pump, and the condensate water is reheated into steam.
Before measuring the circulation multiplying power of the steam generator, the reactor is in a power operation mode, and the unit stably operates on a certain power platform, so that the operation state of the unit needs to be set. Before measurement, equipment and a system needing isolation and a method for realizing isolation are determined, an isolation valve is checked in advance, and if defects are found, the defects are eliminated in time. The chemical content and type of the water in the steam generator, feed water system, main steam system, condensate system should be kept within the allowable range, and all the possibilities leading to the loss of trace substances should be eliminated in advance.
The circulation multiplying power of the steam generator is measured under the full power state of the unit, and the initial state of the unit is set and verified according to the following requirements:
(1) the unit stably operates for at least 24 hours under full power, so that no disturbance of xenon or water supply transient state is ensured, and the thermal power of the unit is close to a rated value as much as possible;
(2) reactor control rods are in automatic mode and do not have boration or dilution operations;
(3) the temperature control rod is in an automatic mode and is within the regulation band;
(4) the main water supply flow and the main steam flow are kept stable;
(5) the water level control of the steam generator is in an automatic mode, and the water level of the steam generator is stable;
(6) the pressure and water level of the pressure stabilizer are controlled in an automatic mode, and the water level of the pressure stabilizer is stable;
(7) the steam turbine operates in a load limiting mode, and the load reference value is 100% of full power;
(8) the condensate pump is in a stable operation state;
(9) the steam generator outlet pressure reaches a rated value;
(10) the temperature of the main feed water of the steam generator is close to a rated value;
(11) the water quality of the second loop of the unit does not exceed the control range of the second operation area;
(12) and isolating the APG and the ATE system.
And measuring the circulation multiplying power of the steam generator on other power platforms, and performing set initial state setting after adaptively modifying according to the requirements.
After the initial state of the unit is set, a tracer can be injected into the second loop of the unit. The invention only needs to sample the liquid phase, and does not need to sample the steam-water mixture. In order to ensure the accuracy of the measurement result, the injected tracer in the embodiment needs to satisfy the following requirements:
(1) readily soluble in water but substantially insoluble in steam (solubility less than 0.1% under the conditions of steam tested);
(2) is not volatilized;
(3) the performance is stable under the circulating working condition of the steam turbine;
(4) not adsorbed on the water film on the inner surface;
(5) in any case, the water can be mixed with the water fully and uniformly.
In addition, while the tracer meets the above requirements, it is also considered that the tracer does not affect the materials in the circulation system and does not pose a hazard to the operating personnel. Sodium, lithium, potassium, cesium salts and the like are therefore generally employed as tracers, determined primarily by the configuration of the particular type of reactor and the background values of the chemical elements in the known feedwater. In view of the maturity and accuracy of ion concentration detection, the present embodiment preferably uses cesium (Cs) ions as a tracer for steam generator cycle rate measurements.
The concentration of the tracer is determined by the injection amount of the tracer and the water content of the steam generator, and the injection amount of the tracer is limited in consideration of the operation safety of the unit. The increase in the conductivity of the cations in the steam generator after tracer injection is generally selected to be less than a zone control value of the unit chemistry operating specification and to have a margin. For example, in the measurement of circulation multiplying power of a steam generator of a certain unit, the control value of the cation conductivity zone of the steam generator is 1.0 mu s/cm, the injection amount of the tracer is 160g of cesium carbonate, and the increase value of the cation conductivity is 0.51 mu s/cm.
In the embodiment, by means of the characteristic that the tracer agent is easily dissolved in water but not dissolved in steam, the circulation multiplying power of the steam generator is calculated and determined by measuring the concentrations of the tracer agent in representative samples at the upper part and the lower part of the steam generator and at a water supply pipeline at the inlet of the steam generator, so that the circulation multiplying power of the steam generator can be accurately measured at any time for the in-service nuclear power generating unit.
Further, in step S1, injecting an appropriate amount of tracer into the second unit loop, so that the tracer flows circularly along the second unit loop, specifically including:
and injecting a tracer agent into a condensate pump inlet of the condensate system or a pipeline of a feedwater flow control system between the feedwater system and the steam generator through a high-pressure injection pump, so that the tracer agent is carried by moisture in saturated steam after entering the steam generator, enters a steam turbine, flows to the feedwater system and then enters the steam generator again for circulation.
It should be noted that after the tracer meeting the requirement is selected, the tracer can be injected into the unit two loop through a temporary device, and the injection positions of the tracer are generally two options, as shown in fig. 2, an injection port a1 and an injection port a 2. The injection port A1 is an inlet of the condensate pump 4, and the tracer is injected into the inlet of the condensate pump, so that the advantages of low injection temperature and pressure and low injection leakage risk are achieved. The injection port A2 is the ARE (feeder flow control System) System pipeline injection port between the water supply System 5 and the steam generator 1, when the tracer is injected into the ARE System pipeline, because the high-temperature high-pressure medium flows in the pipeline, the tracer injection operation has certain difficulty, a high-pressure injection pump needs to be additionally installed, and the tracer injected from the injection port A2 has the advantages that the tracer is not easy to run off and is not easy to precipitate in the water supply pipeline pollution equipment.
The present embodiment preferably injects the tracer from injection port a2 in view of affecting the representativeness and accuracy of the sampled sample.
After the tracer is injected into a second loop of the unit, the tracer flows along a second loop pipeline, enters a steam generator, is only carried by moisture in saturated steam to enter a steam turbine, and returns to a water supply system after being separated by regenerative steam extraction of a high-pressure heater and a steam-water separation reheater and then enters the steam generator again.
Further, the measurement method further includes:
sampling and detecting the concentration of the tracer agent at a drain tank of a steam-water separator reheater system (GSS) and a pipeline of a condensate extraction system (CEX), and tracking the change trend of the concentration of the tracer agent;
and after the concentration of the tracer is stable, judging that the tracer circulates in the second loop of the unit to be stable.
It should be noted that after the tracer passes through a plurality of cycles in the unit two-circuit, the internal cycle of the tracer in the unit two-circuit water supply system and the steam generator body reaches balance, the tracer cycle is stable, the quality of the tracer carried out by the wet steam is equal to the quality of the tracer returned to the steam generator through the two-circuit water supply system, and the follow-up operation can be performed.
The flow at the secondary side of the steam generator forms a natural circulation flow for the inside of the steam generator by the difference in the medium weight of the descending channel 11 and the ascending channel 12. After entering the steam generator, the main feed water flows along a descending channel 11 formed between the tube bundle sleeve and the evaporator cylinder together with the moisture separated by the steam-water separator 13 and the dryer 14 of the steam generator, reaches the evaporator tube plate 15, turns to enter an evaporator ascending channel 12, and receives heat of a loop through a heat exchange tube of the steam generator to be heated and evaporated, as shown in fig. 3. After the tracer is injected, the main feed water provided by the water supply system and carrying the tracer enters the steam generator from the inlet 16, flows along the descending channel 11 together with circulating water carrying the tracer, reaches the tube plate 15, then turns to enter the ascending channel 12 and is heated and evaporated, because the tracer is easily soluble in water and insoluble in steam, the tracer is concentrated in the non-evaporated saturated water on the upper part of the ascending channel 12 in the evaporation process, when the steam flows upwards, the saturated water carrying the tracer is separated by the steam-water separator 13 and the dryer 14 and returns to form circulating water, and continuously enters the descending channel 11 of the steam generator together with the main feed water entering from the inlet 16, and then enters the ascending channel 12 to be heated and evaporated, so that natural circulation is formed.
Further, in step S2, after the cycle is stabilized, the measuring the tracer concentrations at the upper part, the lower part and the feed water inlet of the steam generator respectively includes:
after the circulation is stable, sampling the circulating water at the upper part of the steam generator, the water at the outlet of the descending channel and the main feed water at the feed water inlet respectively;
and respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water.
Specifically, the sampling of the circulating water at the upper part of the steam generator, the moisture at the outlet of the descending channel, and the main feed water at the feed water inlet respectively includes:
communicating a sampling pipeline of a nuclear sampling system in a nuclear power station to an outlet of the descending channel, and sampling moisture at the outlet of the descending channel;
switching a sampling pipeline of the nuclear sampling system to the upper part of the steam generator to sample the circulating water;
sampling the main feed water on a high feed water main pipe through a feed water chemical sampling system in the nuclear power station; the high-pressure water supply main pipe is communicated with a water supply inlet of the steam generator.
It should be noted that the representativeness of the sample directly determines the accuracy and authenticity of the test results. This example requires taking representative samples of the steam generator upper, lower and main water supply lines and testing their tracer concentrations to calculate the circulation rate. Representative Sampling of the Feedwater line can be accomplished by the plant's own SIT System (Feedwater Chemical Sampling System), with the Sampling location on the high Feedwater header, as shown at Sampling point B1 in fig. 2. The Sampling of representative samples from the upper and lower steam generators is carried out by the REN System (Nuclear Sampling System) of the power station itself. The upper steam generator sample is the recycled water returned after the steam-water separation of the wet steam, as shown at sample point B2 in fig. 2 and 3, while the lower steam generator sample is taken from the downcomer outlet (upper surface of the tube sheet), as shown at sample point B3 in fig. 2 and 3.
Most of the nuclear power plant REN system steam generator upper and lower sampling share the same sampling line, so the sampling line needs to be quickly switched to the upper part after the lower downcomer outlet sampling is completed. Because the two ion concentrations are different, formal upper sampling can be carried out after the sampling pipeline is flushed for a certain time after switching, so that the upper sample is representative.
Specifically, the measuring the concentrations of the tracers in the circulating water, the outlet moisture of the descending channel and the main feedwater respectively specifically includes:
and respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water by adopting an inductively coupled plasma mass spectrometry.
It should be noted that, according to the concentration of the tracer and the requirement of detection accuracy, a suitable detection instrument is selected for detecting the concentration of the tracer. Because of the low concentration of the tracer in the representative sample at the main water supply line, ICP-MS mass spectrometry is currently in common use for detection. The upper and lower representative sample concentrations of the steam generator were relatively high and were measured using an ICP-MS mass spectrometer, as well as using a graphite furnace atomic absorption spectrophotometer. In the embodiment, the inductively coupled plasma mass spectrometry is preferably used for detection by using the ICP-MS mass spectrometer, because the detection method has the characteristics of less interference, relatively simple spectral line, low detection limit, wide dynamic linear range and rapid determination, and ensures high precision of the detection result.
Further, in step S3, the calculating and obtaining a circulation rate of the steam generator according to the measured tracer concentration specifically includes:
and calculating to obtain the circulation multiplying power of the steam generator according to the measured concentration of the tracer and based on a tracer mass balance method.
Further, the formula of the tracer mass balance method is as follows:
WfCf+WrCw＝WeCb；
We＝Wr+Wf；
the calculation formula of the circulation multiplying power of the steam generator is as follows:
wherein K is the circulation multiplying power of the steam generator, WmsMain steam flow, WeFor lowering the water flow at the outlet of the channel, WrFlow rate of circulating water, WfIs the main water supply flow rate CbTo reduce the concentration of tracer in the channel outlet water, CwAs tracer concentration in the circulating water, CfIs the concentration of the tracer in the main feedwater.
It should be noted that the formula W of the tracer mass balance method can be derived from the tracer mass balance method, i.e. the mass of the tracer at the outlet of the downcomer equals the mass of the tracer carried by the recirculated saturated water from the steam generator plus the mass of the tracer entering the main feed water at the inlet of the steam generatorfCf+WrCw＝WeCbThe formula is simplified by
Thereby obtaining a calculation formula of the circulation rate of the steam generator
Wherein, the main water supply flow WfWith main steam flow WmsAnd (4) equivalence.
According to the embodiment of the invention, a proper amount of tracer is injected into the two loops of the unit, sampling detection is carried out on the upper part, the lower part and the water supply pipeline of the steam generator after circulation is stable, the concentration of the tracer is obtained, and then the circulation rate value of the steam generator is obtained through calculation, so that the accurate measurement of the circulation rate of the steam generator of the in-service nuclear power unit is realized at any time, the safety hazard to the unit and testers can be effectively avoided, the measurement cost is reduced, and the method has the characteristics of safety, economy, advancement and convenience.
Example two
The embodiment of the invention provides a system for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station, which can realize all the processes of the method for measuring the circulation multiplying power of the vertical steam generator of the pressurized water reactor nuclear power station, and the system comprises the following components in percentage by weight, as shown in fig. 4:
a tracer injection module 41, configured to inject an appropriate amount of tracer into a second unit loop, so that the tracer flows circularly along the second unit loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system;
a tracer concentration measuring module 42 for measuring the tracer concentrations at the upper and lower parts of the steam generator and at the feed water inlet, respectively, after the circulation is stabilized;
and the circulation multiplying power calculation module 43 is configured to calculate and obtain the circulation multiplying power of the steam generator according to the measured tracer concentration.
In addition, the system further comprises a control module 44 for controlling the operation of and data transfer between the tracer injection module 41, the tracer concentration measurement module 42 and the cycle multiplier calculation module 43, respectively.
According to the embodiment of the invention, a proper amount of tracer is injected into the two loops of the unit, sampling detection is carried out on the upper part, the lower part and the water supply pipeline of the steam generator after circulation is stable, the concentration of the tracer is obtained, and then the circulation rate value of the steam generator is obtained through calculation, so that the accurate measurement of the circulation rate of the steam generator of the in-service nuclear power unit is realized at any time, the safety hazard to the unit and testers can be effectively avoided, the measurement cost is reduced, and the method has the characteristics of safety, economy, advancement and convenience.
In summary, the invention provides a method and a system for measuring the circulation ratio of a vertical steam generator of a pressurized water reactor nuclear power station, which have the following good practical effects:
(1) and (4) economic aspect. At present, thermal measurement points on steam generators of in-service nuclear power units and newly-built nuclear power units can not completely meet the measurement requirements of a mass balance method and an enthalpy balance method. If the circulation multiplying power is measured, a measuring point needs to be redesigned and a measuring instrument needs to be installed, so that the cost is high. The invention can measure on the existing thermal measuring points and sampling systems of the unit without adding extra cost and has better economy.
(2) And (4) safety. The mass balance method and the enthalpy balance method need to open a pressure guiding pipe and a temperature sleeve on the steam generator body so as to reduce the strength of the steam generator and reduce the operation safety; moreover, the steam generator is located in a nuclear reactor control area, and during the power-on operation of the unit, the use and maintenance of the measuring points need to enter the control area, which may cause irradiation harm to the life safety of operation or testing personnel. The invention only needs to inject less tracer agent into the unit, and sample and detect, and does not need to open the steam generator to take pressure and enter the unit control area, thereby effectively avoiding the safety hazard to the unit and personnel.
(3) And (4) the progress. The installation of the pressure guide pipeline and the temperature sleeve of the steam generator of the unit needs to be carried out under the condition of overhaul or other shutdown of the unit, is related to nuclear safety, and cannot be carried out at any time. If the device is installed during the overhaul period of the unit, the overhaul period is increased; during non-overhaul period, the unit needs to be shut down manually. This can greatly affect the normal operation of the unit. The invention can finish measurement only by utilizing the existing thermotechnical measuring points, measuring instruments and sampling devices of the unit without additionally installing other thermotechnical measuring points and measuring instruments, thereby facilitating measurement at any time and reducing the unplanned shutdown times of the unit or the shutdown time of the unit.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (7)
1. A method for measuring the circulation multiplying power of a vertical steam generator of a pressurized water reactor nuclear power station is characterized by comprising the following steps:
injecting a proper amount of tracer into a second unit loop, and enabling the tracer to circularly flow along the second unit loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system; after entering the steam generator, the main feed water provided by the feed water system and carrying the tracer flows along the descending channel together with circulating water carrying the tracer, turns to enter the ascending channel after reaching the tube plate and is heated and evaporated, the tracer is concentrated in the non-evaporated saturated water, the non-evaporated saturated water is separated from the water and returns to form circulating water, and the circulating water continuously flows together with the entering main feed water in a circulating manner;
after the circulation is stable, sampling the circulating water at the upper part of the steam generator, the water at the outlet of the descending channel and the main feed water at the feed water inlet respectively; respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water; calculating and obtaining the circulation multiplying power of the steam generator according to the measured concentration of the tracer and based on a tracer mass balance method, wherein the formula of the tracer mass balance method is as follows:
WfCf+WrCw＝WeCb；
We＝Wr+Wf；
the calculation formula of the circulation multiplying power of the steam generator is as follows:
wherein K is the circulation multiplying power of the steam generator, WmsMain steam flow, WeFor lowering the water flow at the outlet of the channel, WrFlow rate of circulating water, WfIs the main water supply flow rate CbTo reduce the concentration of tracer in the channel outlet water, CwAs tracer concentration in the circulating water, CfIs the concentration of the tracer in the main feedwater.
2. The method for measuring the circulation rate of the vertical steam generator of the pressurized water reactor nuclear power station as claimed in claim 1, wherein a proper amount of tracer is injected into the secondary unit loop, so that the tracer flows along the secondary unit loop in a circulating manner, and the method specifically comprises the following steps:
and injecting a tracer agent into a condensate pump inlet of the condensate system or a pipeline of a feedwater flow control system between the feedwater system and the steam generator through a high-pressure injection pump, so that the tracer agent is carried by moisture in saturated steam after entering the steam generator, enters a steam turbine, flows to the feedwater system and then enters the steam generator again for circulation.
3. The method for measuring the circulation rate of the vertical steam generator of the pressurized water reactor nuclear power plant as claimed in claim 2, further comprising:
sampling and detecting the concentration of the tracer at a drain tank of a steam-water separation reheater system and a pipeline of a condensed water extraction system, and tracking the change trend of the concentration of the tracer;
and after the concentration of the tracer is stable, judging that the tracer circulates in the second loop of the unit to be stable.
4. The method for measuring the circulation multiplying power of the vertical steam generator in the pressurized water reactor nuclear power plant as claimed in claim 1, wherein the sampling of the circulating water at the upper part of the steam generator, the moisture at the outlet of the descending channel and the main feed water at the feed water inlet respectively comprises the following steps:
communicating a sampling pipeline of a nuclear sampling system in a nuclear power station to an outlet of the descending channel, and sampling moisture at the outlet of the descending channel;
switching a sampling pipeline of the nuclear sampling system to the upper part of the steam generator to sample the circulating water;
sampling the main feed water on a high feed water main pipe through a feed water chemical sampling system in the nuclear power station; the high-pressure water supply main pipe is communicated with a water supply inlet of the steam generator.
5. The method for measuring the circulation rate of the vertical steam generator of the pressurized water reactor nuclear power plant as claimed in claim 1, wherein the tracer is sodium, lithium, potassium or cesium ions;
after the tracer is injected, the increase in the conductivity of the cations in the steam generator is less than a zone control value of a unit chemistry operating specification.
6. The method for measuring the circulation multiplying power of the vertical steam generator of the pressurized water reactor nuclear power station as claimed in claim 5, wherein the step of respectively measuring the circulating water, the outlet moisture of the descending channel and the concentration of the tracer in the main feed water comprises the following steps:
and respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water by adopting an inductively coupled plasma mass spectrometry.
7. A system for realizing the method for measuring the circulation rate of the vertical steam generator of the pressurized water reactor nuclear power plant according to any one of claims 1 to 6, which is characterized by comprising the following steps:
the tracer injection module is used for injecting a proper amount of tracer into the secondary unit loop to enable the tracer to circularly flow along the secondary unit loop; the second loop of the unit is a loop consisting of a steam generator, a steam turbine, a condensed water system and a water supply system; after entering the steam generator, the main feed water provided by the feed water system and carrying the tracer flows along the descending channel together with circulating water carrying the tracer, turns to enter the ascending channel after reaching the tube plate and is heated and evaporated, the tracer is concentrated in the non-evaporated saturated water, the non-evaporated saturated water is separated from the water and returns to form circulating water, and the circulating water continuously flows together with the entering main feed water in a circulating manner;
the tracer concentration measuring module is used for respectively sampling the circulating water at the upper part of the steam generator, the water at the outlet of the descending channel and the main feed water at the feed water inlet after the circulation is stable; respectively measuring the concentrations of the tracer in the circulating water, the outlet water of the descending channel and the main feed water;
and the circulation multiplying power calculation module is used for calculating and obtaining the circulation multiplying power of the steam generator according to the measured concentration of the tracer and based on a tracer mass balance method, and the formula of the tracer mass balance method is as follows:
WfCf+WrCw＝WeCb；
We＝Wr+Wf；
the calculation formula of the circulation multiplying power of the steam generator is as follows:
wherein K is the circulation multiplying power of the steam generator, WmsMain steam flow, WeFor lowering the water flow at the outlet of the channel, WrFlow rate of circulating water, WfIs the main water supply flow rate CbTo reduce the concentration of tracer in the channel outlet water, CwAs tracer concentration in the circulating water, CfIs the concentration of the tracer in the main feedwater.
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